Structural transitions of a semi-flexible polyampholyte.

Area of Science:

• Polymer Physics
• Soft Matter Physics
• Computational Chemistry

Background:

• Polyampholytes (PAs) are polymers with both positive and negative charges.
• Their conformation and dynamics depend on monomer sequence and chain flexibility.
• Understanding PA behavior is crucial for designing advanced materials.

Purpose of the Study:

• To investigate the structural and dynamical properties of flexible and semi-flexible polyampholytes.
• To explore how charge sequence and bending rigidity influence PA conformations.
• To characterize the dynamics of PAs under varying conditions, including hydrodynamic interactions.

Main Methods:

• Coarse-grained molecular dynamics simulations were employed.
• Analysis included mean-square displacement (MSD) and shape factor calculations.
• The study systematically varied bending rigidity and electrostatic interaction strength (Γe).

Main Results:

• Flexible PAs transition from coil to globule conformations based on charge sequence.
• Distinct dynamics were observed for alternating and charge-segregated sequences, with varying exponents (β) in MSD power-law behavior.
• Semi-flexible PAs exhibited globule, bundle, torus, circular, and hairpin-like conformations depending on rigidity and Γe.

Conclusions:

• The charge sequence is a key determinant of flexible PA conformation and dynamics.
• Hydrodynamic interactions significantly alter PA dynamics, especially for alternating sequences.
• Bending rigidity and electrostatic interactions drive diverse conformational transitions in semi-flexible PAs, offering tunable material properties.